Heat exchangers constructed from sandwiching together three stainless steel plates, spot welding in a regular pattern across the face of the plates, and inflating the plates to expand the passageways between the plates is well known in the art. An example of a condenser unit utilizing an inflated plate heat exchanger is shown in U.S. Pat. No. 4,305,456, owned by the assignee of the present invention. In the condenser unit disclosed in that patent, refrigerant flows through the heat exchanger, and the heat exchanger is immersed in a container of water with a counter flow circulation being set up in the condenser unit to optimize its performance. In the heat exchanger unit disclosed in that patent, a single sheet is folded over to create a horizontal passageway along the upper portion of the sheet which minimizes seams and welds, and also provides a smooth upper surface which minimizes the tendency for any corrosion to occur from impurities collecting at the top of the heat exchanger. As a single sheet is used, a single passageway is formed and only refrigerant flows through the heat exchanger unit. In other applications, a multiple plate construction has been utilized to form separate passageways within the same sheet type exchanger. In these devices, three sheets are utilized with the center sheet or divider plate being of a thicker gauge than the outer sheets such that when inflated, the outer sheets expand away from or "pillow" to increase the size of the passageway and enhance the performance of the heat exchanger. In these applications, the multiple sheet has generally been inflated and formed in a straight orientation, and separate connections provided on opposite sides of the heat exchanger to access the passageways on opposite sides of the central divider plate. With this construction, refrigerant or the like could pass through one passageway while water or any other fluid could flow through the other passageway and the heat exchange take place across the central divider plate.
It is desirable to coil these heat exchange units to simplify its mounting, increase its structural strength, and minimize the space required to mount it on a base plate or the like. However, when coiled and enclosed, access to the passageway along the interior of the coil, and opposite the divider plate, is a problem. Often times, these units are subject to vibration and not just any feed through connection can be utilized as it creates a weak point in the construction of the heat exchanger which can be subject to early failure. Furthermore, the plurality of spot welds and the inflation of the heat exchanger create a pillowed type surface which is very difficult to seal against and does not provide any smooth flat surface for connection.
To solve these and other problems, a flow through connection has been developed by the inventors herein which does not interfere with the integrity of the sandwich plate construction, or the plurality of spot welds, and provides a firm connection to the passageway on the interior of the coil, opposite the divider plate. This connection essentially comprises punching or cutting a hole in the outside plate which is centered over a spot weld, the outside plate not being welded at that specific location. Then, one or two arcuate slots are punched or cut in the center divider plate and around the spot weld. The arcuate slots generally surround the spot weld as if the spot weld were at the center of a circle, and the slots partially form an annular ring therearound. The slots are contained within the envelope of the outer hole so that a tube may be placed directly through the outer hole and on to the center divider plate and welded in position to create a fluid tight seal. The outer plate is itself hammered down against the center divider plate and welded around the hole to seal the outside passageway. Thus there is formed a fluid type connection which feeds through one or two arcuate slots cut or punched in the center divider plate to the interior passageway of the coiled, sandwich tupe heat exchanger without interfering with the symetrical construction of the plate including pillowing around a plurality of spot welds.
The invention may be more fully appreciated by referring to the drawings and description of the preferred embodiment which follows.